Vibration-damping rubber composition

Abstract

The purpose of the present invention is to provide a vibration-damping rubber composition having both excellent low-temperature performance and damping performance.　The vibration-damping rubber composition contains, per 100 parts by mass of a rubber component consisting of one or more diene-based rubbers selected from natural rubber and butadiene rubbers, 20-80 parts by mass of carbon black, and 2-30 parts by mass of an oil, wherein the carbon black has an average particle diameter of 40 nm or smaller and the oil in a DSC examination has an endothermic peak at -60°C or higher. It is preferable that the content of natural rubber in the rubber component of the vibration-damping rubber composition is 30 to 100% by mass.

Description

Vibration-isolation rubber composition

[0001] The present invention relates to a vibration-isolation rubber composition that achieves both excellent low-temperature performance and high loss.

[0002] The development of battery electric vehicles (BEVs) has become active. By shifting to BEVs without a heat source, the need to efficiently control the heat inside the vehicle and develop a heat management module that utilizes heat without waste is also increasing.

[0003] Since the heat management module is composed of a compressor and the like, it becomes a vibration source. Therefore, when mounted on a vehicle, it is necessary to use vibration-isolation rubber for vibration isolation. The vibration-isolation rubber is required to have the performance of reducing vibration in the resonance region: high attenuation (reducing vibration at frequencies after the resonance region: low dynamic magnification). Furthermore, when heat control is performed by the heat pump method, in use in cold regions, it is necessary to fully operate the compressor at low temperature for a certain period of time, and excellent low-temperature characteristics are also required to prevent deterioration of vibration at low temperature.

[0004] Japanese Patent Application Laid-Open No. 2022-118764, Japanese Patent Application Laid-Open No. 2024-041336

[0005] The low-temperature characteristics of rubber depend on the characteristics of the polymer used. Although it is known that the use of a BR polymer with a low Tg is effective, the attenuation performance tends to decrease.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a vibration-isolation rubber composition that achieves both excellent low-temperature performance and attenuation performance.

[0007] As a result of intensive studies to achieve the above object, the present inventor has found that by combining a rubber component consisting only of a diene rubber, carbon black with a specific particle size, and an oil with a relatively high viscosity, a vibration-isolation rubber composition that achieves both excellent low-temperature performance and attenuation performance can be obtained, and thus the present invention has been completed.

[0008] The present invention provides an anti-vibration rubber composition comprising 100 parts by mass of a rubber component consisting solely of diene rubber selected from natural rubber and butadiene rubber, 20 to 80 parts by mass of carbon black, and 2 to 30 parts by mass of oil, wherein the average particle size of the carbon black is 40 nm or less, and the oil has an endothermic peak at -60°C or higher in DSC measurement.

[0009] The present invention also provides a vibration-damping rubber member for an automobile's thermal management module, which is obtained by crosslinking the vibration-damping rubber composition.

[0010] The vibration-damping rubber composition of the present invention contains a rubber component consisting solely of diene rubber selected from natural rubber and butadiene rubber. In other words, the vibration-damping rubber composition of the present invention does not contain non-diene rubber as a rubber component. Because the rubber component consists solely of diene rubber selected from natural rubber and butadiene rubber, the vibration-damping rubber composition of the present invention exhibits excellent low-temperature performance.

[0011] The natural rubber used in this invention may be appropriately selected from known types, such as RSS (Ribbed smoked sheets) and TSR (Technically Specified Rubber).

[0012] The butadiene rubber used in this invention may be any known type that can be appropriately selected and used, but from the viewpoint of low-temperature characteristics, it is preferable to use high-cis-1,4-polybutadiene having a cis-1,4 bond content of 90% or more. Examples of such butadiene rubbers include BR 01, BR T700, BR 730 (manufactured by ENEOS Material Co., Ltd.); Nipol® BR1220 (manufactured by Nippon Zeon Co., Ltd.); and UBEPOL® BR150 (manufactured by UBE Elastomer Co., Ltd.).

[0013] The natural rubber content in the rubber component is preferably 30 to 100% by mass, and particularly preferably 40 to 60% by mass.

[0014] The vibration-damping rubber composition of the present invention preferably contains carbon black with an average particle size of 40 nm or less. Examples of such carbon black include SAF grade, ISAF grade, and HAF grade. More preferably, the average particle size of the carbon black is 10 to 30 nm. Damping performance can be improved by using carbon black with an average particle size in this range.

[0015] The carbon black content is preferably 20 to 80 parts by mass, and more preferably 30 to 70 parts by mass, per 100 parts by mass of rubber component.

[0016] The vibration-damping rubber composition of the present invention preferably contains a relatively high viscosity oil. Specifically, it is preferable to contain an oil that has an endothermic peak at -60°C or higher in DSC measurement, and more preferably an oil that has an endothermic peak between -60°C and -35°C. The pour point of such an oil is usually around -5°C to 0°C.

[0017] The oil content is preferably 2 to 30 parts by mass, and more preferably 10 to 20 parts by mass, per 100 parts by mass of rubber component.

[0018] The vibration-damping rubber composition of the present invention, by using a combination of the above-mentioned specific rubber components, carbon black, and oil, is a vibration-damping rubber composition that achieves both excellent low-temperature performance and damping performance. As an indicator of excellent low-temperature performance, Tg is preferably -40°C or lower, more preferably -45°C or lower, and particularly preferably -47°C or lower. Furthermore, as an indicator of excellent damping performance, the loss coefficient (tanδ) is preferably 0.080 or higher, more preferably 0.090 or higher, and particularly preferably 0.100 or higher.

[0019] In addition to the rubber components, carbon black, and oil described above, the vibration-damping rubber composition of the present invention may contain vulcanizing agents, vulcanization accelerators, vulcanization accelerators, crosslinking agents, and anti-aging agents that are commonly used in vibration-damping rubber compositions.

[0020] Examples of vulcanizing agents include sulfur and sulfur-containing compounds such as alkylphenol disulfide compounds, but in the present invention, the use of sulfur is preferred. The amount of sulfur added is usually 0.1 to 10.0 parts by mass, preferably 0.3 to 5.0 parts by mass, and more preferably 0.5 to 3.0 parts by mass, per 100 parts by mass of the rubber component, in order to maintain the desired basic physical properties such as hardness and tensile strength in good condition. Peroxides such as dialkyl peroxides and peroxyketals can also be used as vulcanizing agents, and in this case, the amount added is usually 1.0 to 10.0 parts by mass, preferably 2.0 to 8.0 parts by mass, per 100 parts by mass of the rubber component.

[0021] Examples of vulcanization accelerators include benzothiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, dibenzothiadyl disulfide, N-cyclohexyl-2-benzothiadylsulfenamide, N-t-butyl-2-benzothiadylsulfenamide, and N-t-butyl-2-benzothiadylsulfenamide; guanidine-based vulcanization accelerators such as diphenylguanidine; and thiraum-based vulcanization accelerators such as tetramethylthiuram disulfide, tetrabutylthiuram disulfide, tetradodecylthiuraum disulfide, tetraoctylthiuraum disulfide, and tetrabenzylthiuraum disulfide. These may be used individually or in combination of two or more. In the present invention, benzothiazole-based vulcanization accelerators can be suitably used. The amount of vulcanization accelerator added is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component, from the standpoint of improving the workability of the vibration-damping rubber and obtaining the desired hardness.

[0022] Examples of vulcanization accelerators include zinc oxide (ZnO) and fatty acids, where the fatty acid may be saturated, unsaturated, linear, or branched, and the number of carbon atoms is not particularly limited. Examples of fatty acids include fatty acids with 1 to 30 carbon atoms, preferably 15 to 30, more specifically, naphthenic acids such as cyclohexanoic acid (cyclohexanecarboxylic acid) and alkylcyclopentanes having side chains, saturated fatty acids such as hexanoic acid, octanoic acid, decanoic acid (including branched carboxylic acids such as neodecanoic acid), dodecanoic acid, tetradecanoic acid, hexadecanoic acid, and octadecanoic acid (stearic acid), unsaturated fatty acids such as methacrylic acid, oleic acid, linoleic acid, and linolenic acid, and resin acids such as rosin, tall oil acid, and abietic acid. These may be used individually or in combination of two or more. In the present invention, zinc oxide and stearic acid can be suitably used. The amount of vulcanization accelerator added is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass, per 100 parts by mass of the rubber component, from the standpoint of improving the workability of the vibration-damping rubber and obtaining the desired hardness.

[0023] Examples of crosslinking agents include bismaleimide compounds and phenolic resins. Examples of bismaleimide compounds include N,N'-o-phenylenebismaleimide, N,N'-m-phenylenebismaleimide, N,N'-p-phenylenebismaleimide, N,N'-(4,4'-diphenylmethane)bismaleimide, 2,2-bis-[4-(4-maleimoidphenoxy)phenyl]propane, and bis(3-ethyl-5-methyl-4-maleimoidphenyl)methane. In the present invention, bismaleimide compounds are preferred from the viewpoint of storage stability. The amount of these bismaleimide compounds blended is preferably 0.5 to 5.0 parts by mass, more preferably 0.5 to 3.0 parts by mass, per 100 parts by mass of the rubber component.

[0024] Examples of anti-aging agents include phenolic anti-aging agents, imidazole anti-aging agents, amine anti-aging agents, and waxes. These may be used individually or in combination of two or more. The amount of anti-aging agent added is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, and even more preferably 1 to 3 parts by mass, per 100 parts by mass of the rubber component.

[0025] In addition, additives such as antioxidants, foaming agents, plasticizers, lubricants, tackifiers, petroleum resins, ultraviolet absorbers, dispersants, compatibilizers, and homogenizers, which are commonly used in rubber products, may be appropriately blended as needed, within the limits that do not impair the effects of the present invention.

[0026] There are no particular restrictions on the method of compounding the above-mentioned components when obtaining the vibration-damping rubber composition of the present invention. All component raw materials may be compounded and kneaded at once, or each component may be compounded and kneaded in two or three stages. When kneading, a kneader such as a roll, internal mixer, or Banbury rotor can be used. Furthermore, when forming into a sheet or strip, known molding machines such as an extruder or press may be used.

[0027] The vibration-damping rubber member for an automobile thermal management module of the present invention is obtained by crosslinking (vulcanizing) the above-described vibration-damping rubber composition. Although not particularly limited, the vibration-damping rubber composition hardens into a vibration-damping rubber member by vulcanization at 140 to 180°C for 5 to 120 minutes. Since this vibration-damping rubber member is made using the above-described vibration-damping rubber composition of the present invention, it can achieve both excellent low-temperature performance and damping performance.

[0028] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0029] [Examples 1-4, Comparative Examples 1-2] Vibration-damping rubber compositions were produced by kneading each component according to the formulations shown in Table 1. The kneading was performed in two stages: first, all materials except sulfur, crosslinking agent, vulcanization accelerator, and vulcanization accelerator were mixed using a Banbury mixer for about 2.5 minutes; and then, sulfur, crosslinking agent, vulcanization accelerator, and vulcanization accelerator were added and mixed using a Banbury mixer at 110°C for about 1 minute.

[0030] <Low-Temperature Characteristics> The obtained vibration-damping rubber composition was press-vulcanized at 155°C for two bouts (T90 x 2) to produce a cylindrical molded body (vibration-damping rubber member) with a diameter of 8 mm and a height of 6 mm. The glass transition temperature (Tg) was measured using this member. Specifically, using TA Instruments' ARES-G2, shear dynamic viscoelasticity measurements were performed in accordance with JIS K 7244-1, with a strain of 0.1% and a frequency of 100 Hz, with temperature dispersion (-60°C to 40°C), to determine the glass transition temperature (Tg). The results are shown in Table 1.

[0031] <Damping Performance> The obtained vibration-damping rubber composition was press-vulcanized at 155°C for 4 bets (T90 x 4) to produce a cylindrical molded body (vibration-damping rubber member) with a diameter of φ30 mm and a height of 30 mm. The loss coefficient (tanδ) was measured using this member. Specifically, in accordance with JIS K6385, in the non-resonant method of the dynamic property measurement test, vibrations with a frequency of 15 Hz and an amplitude of ±0.5 mm were applied to the test piece perpendicular to its axis under a load that deflects by 10% (3 mm), and the dynamic spring constant tanδ was measured. The results are shown in Table 1.

[0032] The details of each component in Table 1 are as follows: Natural rubber: "RSS#4" Butadiene rubber (BR): "UBEPOL BR150" manufactured by UBE Corporation CB1: ISAF grade carbon black, average particle size 20 nm CB2: FEF grade carbon black, average particle size 42 nm OIL1: Oil with an endothermic peak in DSC measurement between -60°C and -35°C OIL2: Oil with an endothermic peak in DSC measurement between -65°C and -50°C OIL3: Oil with an endothermic peak in DSC measurement between -95°C and -80°C Sulfur: "Powdered sulfur" manufactured by Tsurumi Chemical Co., Ltd. Stearic acid: "Stearic acid 50S" manufactured by Shin Nippon Rika Co., Ltd. Wax: "Santite S" manufactured by Seiko Chemical Co., Ltd. Anti-aging agent: "Nocrack 6C" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Zinc oxide: "No. 3 zinc oxide" manufactured by Hakusui Tech Co., Ltd. Vulcanization accelerator 1: "Noxellar TBT" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: "Noxellar NS-F" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0033]

[0034] As shown in Table 1, the vibration-damping rubber compositions of Examples 1 to 4 exhibit excellent low-temperature characteristics, as their Tg is -40°C or lower, and also demonstrate excellent damping performance, as their loss coefficient (tanδ) is large at 0.080 or higher. On the other hand, the vibration-damping rubber composition of Comparative Example 1, which uses carbon black with a large average particle size, and the vibration-damping rubber composition of Comparative Example 2, which uses low-viscosity oil, both exhibit small loss coefficients and poor damping performance.

[0035] According to the present invention, it is possible to provide an anti-vibration rubber composition that achieves both excellent low-temperature performance and damping performance.

Claims

1. A vibration-damping rubber composition comprising 100 parts by mass of a rubber component consisting solely of diene rubber selected from natural rubber and butadiene rubber, 20 to 80 parts by mass of carbon black, and 2 to 30 parts by mass of oil, wherein the average particle size of the carbon black is 40 nm or less, and the oil has an endothermic peak at -60°C or higher in DSC measurement.

2. The vibration-damping rubber composition according to claim 1, wherein the content of natural rubber in the rubber component is 30 to 100% by mass.

3. The vibration-damping rubber composition according to claim 1, wherein the average particle size of the carbon black is 10 to 30 nm.

4. The vibration-damping rubber composition according to any one of claims 1 to 3, for use in a thermal management module of an automobile.

5. A vibration-damping rubber member for an automobile thermal management module, comprising a crosslinked vibration-damping rubber composition according to any one of claims 1 to 3.

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